Prototrophic strains of E. coli will grow on minimal media, while auxotrophic strains will grow on minimal media supplemented with the required molecules.
Hence, the genotypes of the E. coli strains 1 through 4 are:
• strain 1 is arg‾,
• strain 2 is arg‾ met‾,
• strain 3 is prototrophic (i.e.) wild-type, and
• strain 4 is met‾.